1. Field of the Invention
This invention relates to an apparatus and method for sectioning frozen organic tissue samples under cryogenic conditions.
2. Description of Related Art
It is known in the prior art to freeze tissue samples prior to sectioning in order to allow for greater precision in tissue sectioning. For instance, the tissue sample can be frozen to a particular shape prior to sectioning in order to produce tissue sections of a uniform, desired cross-section. Various apparatus, such as that disclosed in U.S. Pat. Nos. 3,204,424 and 3,213,379, have been developed for freezing tissue specimens in preparation for sectioning in a microtome. It is necessary, therefore, to employ a cryostat microtome which maintains the tissue specimen in a frozen state during sectioning. Current cryostat microtomes, such as that disclosed in U.S. Pat. No. 4,548,051, operate in a cold air environment wherein an enclosure maintains a refrigerated cold air environment within which the microtome is housed. Such cold air microtomes suffer from several shortcomings, as explained below.
A microtome is a piece of precision equipment for making very thin sections (1 to 15 .mu.m) from tissue. A microtome may have to section large numbers of tissue samples daily. These tissue samples may contain countless viruses and bacteria. Due to the fact that slicing organic tissue thinly necessarily results in the simultaneous generation of some amount of tissue debris or "dust," slicing of large numbers of tissue samples necessarily results in generation of large amounts of tissue debris. Accordingly, conventional cold-air cryostat microtome arrangements have been found to result in large amounts of tissue debris becoming airborne. This tissue debris contains whatever viruses and bacteria that were present in the original tissue specimen. Thus, one problem associated with prior cryostat microtomes is that some originally pure tissue specimens are contaminated by airborne tissue particles of other specimens, thereby greatly reducing the accuracy of analyses and/or examinations of such tissue sections.
Also, due to the precision required in producing such thinly sliced tissue sections, close operator supervision is necessary. Thus, in using conventional cryostat microtomes, operators are required to be exposed to the airborne tissue particles generated upon tissue sectioning. There is, accordingly, a great fear of operator contamination from the viruses and bacteria present in these airborne particles. This fear has been particularly accentuated in recent years by increased cases of hepatitis and AIDS. Thus, operators are currently reluctant to operate conventional microtomes or work near them.
Current microtomes generate significant amounts of tissue debris during sectioning. Thus, there is a need for the ability, in such microtomes, to be able to section large quantities of tissue without allowing the tissue debris generated therewith to become airborne.